This invention relates generally to well production technology and more particularly concerns guides used to center sucker rods in well production tubing and to remove paraffin from the inner surface of the tubing.
Oil wells typically have a depth in a range of several hundred to several thousand feet. Sucker rods, each 25′ to 30′ long and ⅝″ to 1⅛″ inches in diameter, are linked together inside production tubing with a 2″ to 3″ inches inside diameter between an above-ground reciprocating jack and a bottom hole pump.
Deviation of the well components from vertical is a well-recognized problem. The production tubing axial alignment is going to deviate from vertical over its depth and the greater the well depth the more likely and more serious the deviation. The sucker rod string axial alignment is going to deviate from vertical between the jack and the pump because the pump reciprocation is delayed in comparison to the jack reciprocation. Whatever the cause, the deviation renders the rods, the rod couplings and the production tubing vulnerable to metal-to-metal frictional wear during well operation. Centering the sucker rods in the production tubing reduces such frictional wear.
Congealing paraffin is another well-recognized problem. In many oil wells, paraffin that remains mixed with warm-hot crude oil congeals as the oil cools while rising to the surface. The congealed paraffin coats the rods and the tubing and clogs the product flow paths. Removal of paraffin from the tubing wall increases the throughput of product from the well.
Sucker rod guides been devised for centering sucker rods inside their tubing and acting as a bushing to smooth out the pumping action. Some of these guides also serve the added purpose of scraping the tubing wall to break clogs and maintain acceptable rates of flow of product from the well. Some are made of plastic suitable to withstand hostile well conditions including high temperatures, harsh chemicals, sand or particulates, and even electrolysis. The problem with known sucker rod guides is that one of their primary purposes, maintaining high productivity, is often compromised in deference to another primary purpose, long-term operation.
As an example, if a guide does not adequately scrape the paraffin from the tubing, the tubing will eventually clog and reduce or cease production. In order to achieve adequate long term scraping, more and/or wider radial ribs are incorporated in the guide so as to increase its scraping circumference on the tubing. But incorporation of more and/or wider ribs structurally decreases the cross-sectional area of the product flow paths, reducing productivity. Thus, the benefit of increased production gained by better scraping is offset by lost production due to structurally constricted flow.
In another example, if a guide does not grip its rod securely enough to prevent it from sliding on its rod, its scraping benefit is sooner or later diminished or lost. In order to maintain longer grip security, the guide length is generally increased to increase its rod gripping surface. But a longer guide increases the drag on product flow through the guide, reducing productivity. Thus the benefit of increased production gained by longer connection between the guide and the rod is offset, once again by lost production due to structurally constricted flow.
It is, therefore, a primary object of this invention to provide a sucker rod guide which assists in maintaining an acceptable, long-term rate of product flow in a well production tubing.
It is also an object of this invention to provide a sucker rod guide which simultaneously affords a higher tubing contact area and a higher flow cross-sectional area than known guides.
It is another object of this invention to provide a sucker rod guide which simultaneously affords a higher flow cross-sectional area to guide length ratio than known guides.